1. Field of the Invention
The present invention relates to a lithium ion capacitor, and more particularly, to a method of manufacturing a lithium ion capacitor in which a lithium ion pre-doping process of an anode is performed using a separator having a lithium thin film disposed on one surface thereof, and a lithium ion capacitor manufactured using the same.
2. Description of the Related Art
In general, electrochemical energy storage devices are core parts of end-products, which are essentially used in mobile information communication devices, and mobile electronic devices. In addition, the electrochemical energy storage devices will be securely used as high quality energy sources in a renewable energy system that can be applied to future electric vehicles, mobile electronic terminals, and so on.
An electrochemical capacitor, among the electrochemical energy storage devices, may be classified as an electrical double layer capacitor using an electrical double layer theory and a hybrid supercapacitor using electrochemical oxidation-reduction reaction.
Here, while the electrical double layer capacitor is widely used in a field in which high output energy characteristics are needed, the electrical double layer capacitor has problems such as a small capacity, and so on. On the other hand, research on the hybrid supercapacitor is actively performed to improve capacitive characteristics of the electrical double layer capacitor.
In particular, a lithium ion capacitor (LIC), among the hybrid supercapacitors, has an anode doped with lithium ions to have a charge capacity three to four times of the electrical double layer capacitor, providing large energy density.
Here, in a process of pre-doping an anode with lithium ions, lithium metal films are disposed on an uppermost layer and a lowermost layer of an electrode cell, and then, the electrode cell is immersed in an electrolyte. At this time, since the lithium films are disposed on both ends of the electrode cell, lithium ions may be non-uniformly doped to the laminated anode. In addition, since the lithium metal film may remain after the pre-doping process, lithium metal may be extracted during an operation of the lithium ion capacitor to decrease reliability of the lithium ion capacitor.
Further, since about twenty days are required until the lithium ions are uniformly doped to the anode provided in the electrode cell, it is difficult to apply the process to mass production. That is, while the lithium ion capacitor needs a pre-doping process to the anode to improve capacitive characteristics, reliability of the lithium ion capacitor may be decreased due to the pre-doping process to the anode or it is difficult to apply the process to mass production.
Therefore, in order to apply the lithium ion capacitor having high capacity to mass production, a new anode pre-doping process capable of uniformly and rapidly doping lithium ions to the anode is needed.